The Idea -Our project looks to create a battery powered bluetooth amplifier for regular everyday home speakers. While there are bluetooth speakers out in the market, for those who have bookshelf speakers, or towers in their home setup, they can repurpose their speakers on the go by using this device. For speakers with banana plugs, you can easily unplug your speakers and connect this device to use on the go.

The Inspiration - I thought of this idea when I was going to dance practice and we used a $80 bluetooth speaker, 2x10w woofers. Although it is small, the downside is that there is not a big enough cabinet to reproduce low end sound. Also, most bluetooth speakers I have listened to from Bose, JBL, and Harmon Kardon have very muddy mids or highs due to them not using tweeters.

“Portability” comes to mind when developing this idea. However, for this case, portability just entails that we can move the device without hassle and leave it in place once it is setup. For example, carrying the speaker to the gym, park, or dance practice room.

So I thought, my speakers at home are pretty nice, however I’d have to remove my receiver which requires my to disconnect my entire setup. So I thought about how easy it is to unplug and replug in banana plugs and thought it would be interesting to make a portable amp that supports these connections. Of course for older speakers without banana plugs, they can remove the banana plugs and connect the cable directly to the speaker clips.

The bluetooth chip we are looking into is the CC2564MODN or the CC2564MODA from TI. The difference between the two is that one has an integrated chip antenna and the other allows us to use our own antenna, for example a pcb printed antenna. However, this selection requires more research depending on the chassis.

The amp/dac that we are looking for is one that can operate with 20~40w @8ohm mono with an i2S, Inter-IC Sound, bus to communicate with the bluetooth chip. We would use the bluetooth chip as the master clock, and send its clock to the dac as a slave. We are also looking at a Class D amplifier due to it having a better efficiency than AB amplifiers. Although this causes more distortion, it should be above frequency ranges above audible levels. We are looking to ask TI if we can get 5 evaluation modules for their next gen series chip as they currently are in pre-production, but in the meantime we will purchase something like a TAS5731PHP as we don't know the turnaround time/cost for a new chip.

The Battery -The battery needs to have a decent capacity and maximum output power, while also not being too heavy to carry around. Small sealed lead acid batteries (SLA) typically found in uninterrupted power supplies (UPS) would work, although they are usually very heavy for their capacity. Instead, we would use lithium batteries, which have good energy density and output power while also being lightweight. We will also integrate charging of the battery into the device using a lithium charging circuit, like TI’s BQ24616 chip.

The Housing -For the chassis, we are looking at having a plastic housing for the device to reduce capturing noise. However, we do notice that although class D amps are efficient, there is still heat that needs to be dissipated. Assuming 94% efficiency according to Texas Instruments’ TPA3244 Amp chip, we can expect about 2.4 watts of heat from the chip itself. If using the PCB as a heatsink is not sufficient with passive cooling (slits through the chassis), we can look at creating a metal chassis with an external bluetooth antenna, or have a low rpm fan to move airflow inside of the chassis.

Low Cost Myoelectric Prosthetic Hand

Michael Fatina, Jonathan Pan-Doh, Edward Wu

Featured Project

According to the WHO, 80% of amputees are in developing nations, and less than 3% of that 80% have access to rehabilitative care. In a study by Heidi Witteveen, “the lack of sensory feedback was indicated as one of the major factors of prosthesis abandonment.” A low cost myoelectric prosthetic hand interfaced with a sensory substitution system returns functionality, increases the availability to amputees, and provides users with sensory feedback.

We will work with Aadeel Akhtar to develop a new iteration of his open source, low cost, myoelectric prosthetic hand. The current revision uses eight EMG channels, with sensors placed on the residual limb. A microcontroller communicates with an ADC, runs a classifier to determine the user’s type of grip, and controls motors in the hand achieving desired grips at predetermined velocities.

As requested by Aadeel, the socket and hand will operate independently using separate microcontrollers and interface with each other, providing modularity and customizability. The microcontroller in the socket will interface with the ADC and run the grip classifier, which will be expanded so finger velocities correspond to the amplitude of the user’s muscle activity. The hand microcontroller controls the motors and receives grip and velocity commands. Contact reflexes will be added via pressure sensors in fingertips, adjusting grip strength and velocity. The hand microcontroller will interface with existing sensory substitution systems using the pressure sensors. A PCB with a custom motor controller will fit inside the palm of the hand, and interface with the hand microcontroller.